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Chiral Magnetic Effect in Isobar Collisions from Stochastic Hydrodynamics
Gui-Rong Liang, Jinfeng Liao, Shu Lin, Li Yan, Miao Li
Published:   , doi: 10.1088/1674-1137/44/9/094103
We study chiral magnetic effect in collisions of AuAu, RuRu and ZrZr at \begin{document}$\sqrt{s_{\rm{NN}}}=200\;{\rm{GeV}}$\end{document}. The axial charge evolution is modeled with stochastic hydrodynamics and geometrical quantities are calculated with Monte Carlo Glauber model. By adjusting the relaxation time of magnetic field, we find our results in good agreement with background subtracted data for AuAu collisions at the same energy. We also make prediction for RuRu and ZrZr collisions. We find a weak centrality dependence of initial chiral imbalance, which implies the centrality dependence of chiral magnetic effect signal comes mainly from those of magnetic field and volume factor. Our results also show an unexpected dependence on system size: while the system of AuAu has larger chiral imbalance and magnetic field, it turns out to have smaller signal for chiral magnetic effect due to the larger volume suppression factor.
The fine micro-thermal structures for the Reissner-Nordström black hole
Zhen-Ming Xu, Bin Wu, Wen-Li Yang
Published:   , doi: 10.1088/1674-1137/44/9/095106
Based on the idea of the black hole molecule proposed in [Phys. Rev. Lett. 115 (2015) 111302], in this paper, by choosing the appropriate extensive variables, we have solved the puzzle whether the molecules of the Reissner-Nordström black hole is an interaction or not through the Ruppeiner thermodynamic geometry. Our results show that the Reissner-Nordström black hole is indeed an interaction system that may be dominated by repulsive interaction. More importantly, with the help of a new quantity, thermal-charge density, we describe the fine micro-thermal structures of the Reissner-Nordström black hole in detail. It presents three different phases, the free, interactive and balanced phases. The thermal-charge density plays a role similar to the order parameter, and the back hole undergoes a new phase transition between the free phase and interactive phase. The competition between the free phase and interactive phase exists, which leads to the extreme behavior of the temperature of the Reissner-Nordström black hole. For extreme Reissner-Nordström black hole, the whole system is completely in the interactive phase. What is more significant is that we provide the thermodynamic micro-mechanism for the formation of the naked singularity of the Reissner-Nordström black hole.
Strong gravitational lensing for photon coupled to Weyl tensor in Kiselev black hole
G. Abbas, Asif Mahmood, M. Zubair
Published:   , doi: 10.1088/1674-1137/44/9/095105
The ambition of the present work is to highlight the phenomena of strong gravitational lensing and deflection angle for the photons coupling with Weyl tensor in a Kiselev black hole. Here, we have extended the prior work of Chen and Jing [1] for Schwarzschild black hole to Kiselev black hole. For this purpose, the equation of motion for the photons coupled to Weyl tensor, null geodesic and equation of photon sphere in a Kiselev black hole spacetime have been formulated. It is found that the equation of motion of the photons depends not only on the coupling between photon and Weyl tensor, but also on the polarization direction of the photons. There is a critical value of the coupling parameter \begin{document}$ \alpha$\end{document} for existence of the marginally circular photon orbit outside the event horizon, which depends on the parameters of black hole and the polarization direction of photons. Further, the polarization directions of coupled photon and the coupling parameter \begin{document}$ \alpha$\end{document}, both modify the features of the photon sphere, the angle of deflection and the functions \begin{document}$ (\bar{a}$\end{document} and \begin{document}$ \bar{b})$\end{document} for the strong gravitational lensing in Kiselev black hole spacetime. In addition to this, the observable gravitational lensing quantities and the shadows of the Kiselev black hole spacetime are presented in detail.
Systematic study of the $\alpha$ decay preformation factor of nuclei around the ${Z=82}$, ${N=126}$ shell closures within a generalized liquid drop model
Hong-Ming Liu, You-Tian Zou, Xiao Pan, Xiao-Jun Bao, Xiao-Hua Li
Published:   , doi: 10.1088/1674-1137/44/9/094106
In this work, we systematically study the \begin{document}$\alpha$\end{document} decay preformation factors \begin{document}$P_{\alpha}$\end{document} and \begin{document}$\alpha$\end{document} decay half-lives of 152 nuclei around Z = 82, N = 126 closed shells based on a generalized liquid drop model while \begin{document}$P_{\alpha}$\end{document} is extracted from the ratio of the calculated \begin{document}$\alpha$\end{document} decay half-life to the experimental one. The results show that there is an obvious linear relationship between \begin{document}$P_{\alpha}$\end{document} and the product of valance protons (holes) \begin{document}$N_p$\end{document} and valance neutrons (holes) \begin{document}$N_n$\end{document}. At the same time, we extract the \begin{document}$\alpha$\end{document} decay preformation factors values of even-even nuclei around Z = 82, N = 126 closed shells from the work of Sun \begin{document}${et\ al.}$\end{document} [J. Phys. G: Nucl. Part. Phys. 45, 075106 (2018)], in which the \begin{document}$\alpha$\end{document} decay preformation factors can be calculated by two different microscopic formulas. We find that the \begin{document}$\alpha$\end{document} decay preformation factors are also related to \begin{document}$N_pN_n$\end{document}. Combining with our previous works [Sun \begin{document}${et\ al.}$\end{document}, Phys. Rev. C 94, 024338 (2016); Deng \begin{document}${et\ al.}$\end{document}, ibid. 96, 024318 (2017); Deng \begin{document}${et\ al.}$\end{document}, ibid. 97, 044322 (2018)] and the work of Seif \begin{document}${et\ al.}$\end{document} [Phys. Rev. C 84, 064608 (2011)], we suspect that this phenomenon of linear relationship for the nuclei around those closed shells is model independent. It may be caused by the effect of the valence protons (holes) and valence neutrons (holes) around the shell closures. Finally, using the formula obtained by fitting the \begin{document}$\alpha$\end{document} decay preformation factor data calculated by the generalized liquid drop model (GLDM), we calculate the \begin{document}$\alpha$\end{document} decay half-lives of these nuclei. The calculated results are agree with the experimental data well.
Isospin dependence of the projectile fragmentation at hundreds MeV/nucleon
Jun Su, Long Zhu, Chenchen Guo, Feng-Shou Zhang
Published:   , doi: 10.1088/1674-1137/44/9/094105
By modeling the fragmentation process with the dynamics model and permitting only evaporation in a statistical code, the main features of the projectile fragmentation at 600 MeV/nucleon were studied in our previous work [Phys. Rev. C, 98: 014610 (2018)]. In this work, we continue and extend it to the isospin dependence of the projectile fragmentation at several hundreds MeV/nucleon. We devote ourselves to searching for isospin observables related to the isospin fractionation to extract the symmetry energy. It is found that at the pre-equilibrium stage of the collisions, the isospin diffusion will take place and affect the isospin of the final fragments. At the fragmenting stage, the isospin fractionation plays a part. Comparing to the soft symmetry energy, the stiff one provides smaller repulsive force for neutrons and attractive force for the protons in the neutron rich system at subnormal density, and hence causes smaller isospin asymmetry of the gas phase, leaving a more neutron rich liquid phase. The robust isospin observable is proposed for extracting the slope of the symmetry energy at the normal density by the isospin dependence of the projectile fragmentation at hundreds MeV/nucleon.
Rare $\Lambda_b \rightarrow \Lambda l^+ l^- $ decay in the Bethe-Salpeter equation approach
Liang-Liang Liu, Xian-Wei Kang, Zhen-Yang Wang, Xin-Heng Guo
Published:   , doi: 10.1088/1674-1137/44/8/083107
We study the rare decays \begin{document}$\Lambda_b \rightarrow \Lambda l^+ l^-~(l=e,\mu, \tau)$\end{document} in the Bethe-Salpeter equation approach. We find that the branching ratio \begin{document}$Br(\Lambda_b \rightarrow \Lambda \mu^+ \mu^-)\times 10^{6} = 1.051 \sim 1.098$\end{document} in our model. This result agrees with the experimental data well. In the same parameter regions, we find that the branching ratio \begin{document}$Br(\Lambda_b \rightarrow \Lambda e^+ e^-(\tau^+ \tau^-) )\times 10^{6} = 0.252 \sim 0.392 ~(0.286 \sim 0.489)$\end{document}.
A Lattice Study of the Two-photon Decay Widths for Scalar and Pseudo-scalar Charmonium
Ying Chen, Ming Gong, Ning Li, Chuan Liu, Yu-Bin Liu, Zhaofeng Liu, Jian-Ping Ma, Yu Meng, Chao Xiong, Ke-Long Zhang
Published:   , doi: 10.1088/1674-1137/44/8/083108
In this exploratory study, two photon decay widths of pseudo-scalar (\begin{document}$ \eta_c $\end{document}) and scalar (\begin{document}$ \chi_{c0} $\end{document}) charmonium are computed using two ensembles of \begin{document}$ N_f = 2 $\end{document} twisted mass lattice QCD gauge configurations. The simulation is performed two lattice ensembles with lattice spacings \begin{document}$ a = 0.067 $\end{document} fm with size \begin{document}$ 32^3\times{64} $\end{document} and \begin{document}$ a = 0.085 $\end{document} fm with size \begin{document}$ 24^3\times{48} $\end{document}, respectively. The results for the decay widths for the two charmonia are obtained which are in the right ballpark however smaller than the experimental ones. Possible reasons for these discrepancies are discussed.
Perturbation solutions of relativistic viscous hydrodynamics for longitudinally expanding fireballs
Ze-Fang Jiang, Duan She, C. B. Yang, Defu Hou
Published:   , doi: 10.1088/1674-1137/44/9/094107
The solutions of relativistic viscous hydrodynamics for longitudinal expanding fireballs is investigated with the Navier-Stokes theory and Israel-Stewart theory. The energy and Euler conservation equations for the viscous fluid are derived in Rindler coordinates with the longitudinal expansion effect is small. Under the perturbation assumption, an analytical perturbation solution for the Navier-Stokes approximation and numerical solutions for the Israel-Stewart approximation are presented. The temperature evolution with both shear viscous effect and longitudinal acceleration effect in the longitudinal expanding framework are presented and specifically temperature profile shows symmetry Gaussian shape in the Rindler coordinates. In addition, in the presence of the longitudinal acceleration expanding effect, the results of the Israel-Stewart approximation are compared to the results from the Bjorken and the Navier-Stokes approximation, and it gives a good description than the Navier-Stokes theories results at the early stages of evolution.
Exclusive photoproduction of vector meson at next-to-leading order from Color Glass Condensate
Yanbing Cai, Wenchang Xiang, Mengliang Wang, Daicui Zhou
Published:   , doi: 10.1088/1674-1137/44/7/074110
The exclusive photoproduction of vector mesons (\begin{document}$J/\psi$\end{document} and \begin{document}$\phi$\end{document}) are investigated by taking into account the next-to-leading order corrections in the framework of Color Glass Condensate. We confront the next-to-leading order modified dipole amplitude with the HERA data finding good agreement. Our studies show that the \begin{document}$\chi^2/d.o.f$\end{document} from leading order, running coupling and collinearly improved next-to-leading order dipole amplitudes are 2.159, 1.097, and 0.932 for the elastic cross section, and 2.056, 1.449, and 1.357 for the differential cross section. The outcomes indicate that the higher-order corrections have a significant contribution to the vector meson productions and the description of the experimental data is dramatically improved once the higher order corrections are included. We extend the next-to-leading order exclusive vector meson production model to LHC energies by using the same parameters obtained from HERA. We find that our model can also give a rather good description of the \begin{document}$J/\psi$\end{document} and \begin{document}$\phi$\end{document} data in proton-proton collision at 7 TeV and 13 TeV at LHCb experiments.
The running curvaton
Qin Chang, Xiao-Lin Wang, Li-Ting Wang
Published:   , doi: 10.1088/1674-1137/44/8/085103
Inspired by [1], we propose a similar curvaton mechanism whose realization occurs in preheating process, in which the effective mass is running (its potential consists of coupling part and exponential part whose contribution is subdominant comparing to the coupling part). The production of curvaton contains the cases of narrow resonance and broad resonances whose criteria comes via the spectral index of curvaton. Since the inflationary potential is chaotic inflation (quadratic potential), it could smoothly transit into the preheating process. Once the entropy perturbation transferred into curvature perturbation, we will use \begin{document}$ \delta N $\end{document} formalism to investigate its validity. By neglecting the contribution of exponential potential of curvaton, we calculate power spectrum \begin{document}$ P_\zeta $\end{document} and non linear Non-Gaussian parameter \begin{document}$ f_{NL} $\end{document}. Our calculation analytically shows that these two observables are independent of potential of inflaton. Finally, as the curvaton almost decay (inflaton field vanishes), the exponential potential will be approaching a constant of order of cosmological constant, which may play a role of dark energy.
Redshift drift in uniformly accelerated reference frame
Zhe Chang, Qing-Hua Zhu
Published:   , doi: 10.1088/1674-1137/44/7/075103
We construct an alternative uniformly accelerated reference frames based on 3+1 formalism in adapted coordinates. In this frames, there is time-dependent redshift drift between co-moving observers, which is different from that in the Rindler coordinates. It can be tested in laboratory and promote our understanding for non-inertial frames.
Quark-hadron phase transition in DGP including BD brane
Tayeb Golanbari, Terife Haddad, Abolhassan Mohammadi, M. A. Rasheed, Kh. Saaidi
Published:   , doi: 10.1088/1674-1137/44/8/083109
A DGP brane-world model with a perfect fluid brane matter including a Brans-Dicke (BD) scalar field on brane has been utilized to investigate the problem of the quark-hadron phase (QHP) transition in early times of the Universe evolution. The presence of the BD scalar field comes up with some modification terms in the Friedmann equation. Since the behavior of phase transition strongly depends on the basic evolution equations, even a small change in these relations might come to interesting results about the time of transition. The phase transition is investigated using two scenarios of the first-order phase transition and smooth crossover phase transition. For first-order scenario, which is used for intermediate temperature regime, the evolution of the physical quantities, such as temperature and scale factor, are investigated before, during and after the phase transition. The results show that the transition occurs in about micro-second. In the next part, the phenomenon is studied by assuming a smooth crossover transition where the lattice QCD data is utilized to obtain a realistic equation of state for the matter. The investigation for this part is performed in two regimes of high and low-temperature. Using trace anomaly in the high-temperature regime specifies a simple equation of state which states that the quark-gluon behaves like radiation. However, in the low-temperature regime, the trace anomaly is affected by discretization effects, and the hadron resonance gas model is utilized instead. Using this model, a more realistic equation of state could be found in the low-temperature regime. The crossover phase transition in both regimes is considered. The results determine that the transition occurs at the time around a few micro-second. Also, it is realized that the transition in the low-temperature regime occurs after the transition in the high-temperature regime.
Observational Constraints on the Rastall gravity from Rotation Curves of Low Surface Brightness Galaxies
Meirong Tang, Zhaoyi Xu, Jiancheng Wang
The Rastall gravity is a modification of Einstein's general relativity, in which the energy-momentum conservation is not satisfied and depends on the gradient of the Ricci curvature. It is in dispute whether the Rastall gravity is equivalent to the general relativity (GR). In this work, we constrain the theory using the rotation curves of Low Surface Brightness (LSB) spiral galaxies. Through fitting the rotation curves of LSB galaxies, we obtain the parameter \begin{document}$\beta$\end{document} of the Rastall gravity. The \begin{document}$\beta$\end{document} values of LSB galaxies satisfy Weak Energy Condition (WEC) and Strong Energy Condition(SEC). Combining the \begin{document}$\beta$\end{document} values of type Ia supernovae and gravitational lensing of elliptical galaxies on the Rastall gravity, we conclude that the Rastall gravity may be equivalent to the general relativity.
2νββ-decay to first 2+ state with partial isospin symmetry restoration from spherical QRPA calculations
Dong-Liang Fang, Amand Faessler
Published:   , doi: 10.1088/1674-1137/44/8/084104
With partially restored isospin symmetry, we calculate the nuclear matrix element for a special decay mode of 2νββ (two neutrino double beta decay) – the decay to the first 2+ excited states. With the realistic CD-Bonn nuclear force, we analyze the dependence of the nuclear matrix elements on the iso-vector and iso-scalar parts of proton-neutron particle-particle interaction. The dependence on the different nuclear matrix element is observed and the results are explained. We also give the phase space factors with numerical electron wave functions and properly chosen excitation energies. Finally we give our results for the half-lives of this decay mode for different nuclei.
Study of single-particle resonant states with Green’s function method
C. Chen, Z. P. Li, Y.-X. Li, T.-T. Sun
Published:   , doi: 10.1088/1674-1137/44/8/084105
The relativistic mean field theory with the Green's function method is taken to study the single-particle resonant states. Different from our previous work [Phys.Rev.C 90,054321(2014)], the resonant states are identified by searching for the poles of Green's function or the extremes of the density of states. This new approach is very effective for all kinds of resonant states, no matter it is broad or narrow. The dependence on the space size for the resonant energies, widths, and the density distributions in the coordinate space has been checked and it is found very stable. Taking \begin{document}$ ^{120} $\end{document}Sn as an example, four new broad resonant states \begin{document}$ 2g_{7/2} $\end{document}, \begin{document}$ 2g_{9/2} $\end{document}, \begin{document}$ 2h_{11/2} $\end{document} and \begin{document}$ 1j_{13/2} $\end{document} are observed, and also the accuracy for the width of the very narrow resonant state \begin{document}$ 1h_{9/2} $\end{document} is highly improved to be \begin{document}$ 1\times 10^{-8} $\end{document} MeV. Besides, our results are very close to those by the complex momentum representation method and the complex scaling method.
Identify the hidden charm pentaquark signal from non-resonant background in electron-proton scattering
Zhi Yang, Xu Cao, Yu-Tie Liang, Jia-Jun Wu
Published:   , doi: 10.1088/1674-1137/44/8/084102
We study the electroproduction of the LHCb pentaquark states with the assumption that they are resonant states. The main concern here is to investigate the final state distribution in the phase space in order to extract the feeble pentaquark signal from the large non-resonant background. Our results show that the ratio of the signal to background would increase significantly with proper kinematic cut, which would be very helpful for future experimental analysis.
Phenomenological Advantages of the Normal Neutrino Mass Ordering
Shao-Feng Ge, Jing-yu Zhu
Published:   , doi: 10.1088/1674-1137/44/8/083103
The preference of the normal neutrino mass ordering from the recent cosmological constraint and the global fit of neutrino oscillation experiments does not seem like a wise choice at first glance since it obscures the neutrinoless double beta decay and hence the Majorana nature of neutrinos. Contrary to this naive expectation, we point out that the actual situation is the opposite. The normal ordering opens the possibility of excluding the higher solar octant and simultaneously measuring the two Majorana CP phases in future \begin{document}$0 \nu 2 \beta$\end{document} experiments. Especially, the funnel region will completely disappear if the solar mixing angle takes the higher octant. The combined precision measurement by the JUNO and Daya Bay experiments can significantly reduce the uncertainty in excluding the higher octant. With a typical \begin{document}${\cal{O}}({\rm{meV}})$\end{document} sensitivity on the effective mass \begin{document}$|m_{ee}|$\end{document}, the neutrinoless double beta decay experiment can tell if the funnel region really exists and hence exclude the higher solar octant. With the sensitivity further improved to sub-meV, the two Majorana CP phases can be simultaneously determined. The normal neutrino mass ordering clearly shows phenomenological advantages than the inverted one.
Tensor form factors of PP, S, V and A transitions within the standard and the covariant light-front approaches
Qin Chang, Xiao-Lin Wang, Li-Ting Wang
Published:   , doi: 10.1088/1674-1137/44/8/083105
In this paper, we investigate the tensor form factors of \begin{document}$ P\to P,\,S,\,V $\end{document} and A transitions within the standard light-front (SLF) and the covariant light-front (CLF) quark models (QMs). The self-consistency and Lorentz covariance of CLF QM are analyzed via these quantities, and the effects of zero-mode are discussed. For the \begin{document}$ P\to V $\end{document} and A transitions, besides the inconsistence between the results extracted via longitudinal and transverse polarization states, which is caused by the residual \begin{document}$ \omega $\end{document}-dependent spurious contributions, we find and analyze a “new” self-consistence problem of the traditional CLF QM, which is caused by the different strategies for dealing deal with the trace term in CLF matrix element. A possible solution to the problems of traditional CLF QM is discussed and confirmed numerically. Finally, the theoretical predictions for the tensor form factors of some \begin{document}$ c\to q,\,s $\end{document} and \begin{document}$ b\to q,\,s\,,c $\end{document} (\begin{document}$ q = u,d $\end{document}) induced \begin{document}$ P\to P,\,S,\,V $\end{document} and A transitions are updated within the CLF QM with a self-consistent scheme.
Hadronic cross section of ${e^+e^-}$ annihilation at bottomonium energy region
Xiang-Kun Dong, Xiao-Hu Mo, Ping Wang, Chang-Zheng Yuan
Published:   , doi: 10.1088/1674-1137/44/8/083001
The Born cross section and dressed cross section of \begin{document}$ e^+e^-\to b\bar{b} $\end{document} and the total hadronic cross section in \begin{document}$ e^+e^- $\end{document} annihilation in the bottomonium energy region are calculated based on the \begin{document}$ R_b $\end{document} values measured by the BaBar and Belle experiments. The data are used to calculate the vacuum polarization factors in the bottomonium energy region, and to determine the resonant parameters of the vector bottomonium(-like) states, the \begin{document}$ Y(10750) $\end{document}, \begin{document}$ \Upsilon(5S) $\end{document}, and \begin{document}$ \Upsilon(6S) $\end{document}.
Top-quark pair production at complete-NLO accuracy with NNLO+NNLL′ corrections in QCD
Michał Czakon, Andrea Ferroglia, Alexander Mitov, Davide Pagani, Andrew S. Papanastasiou, Benjamin D. Pecjak, Darren J. Scott, Ioannis Tsinikos, Xing Wang, Li Lin Yang, Marco Zaro
Published:   , doi: 10.1088/1674-1137/44/8/083104
We describe predictions for top-quark pair differential distributions at hadron colliders, which combine the NNLO QCD calculations and NLO electroweak corrections together with double resummation at NNLL′ accuracy of threshold logarithms and small-mass logarithms. This is the first time that such a combination has appeared in the literature, which incorporates all known perturbative information. Numerical results are presented for the invariant-mass distribution, the transverse-momentum distribution as well as rapidity distributions.
QCD phase diagram at finite isospin chemical potential and temperature in an IR-improved soft-wall AdS/QCD model
Xuanmin Cao, Hui Liu, Danning Li, Guanning Ou
Published:   , doi: 10.1088/1674-1137/44/8/083106
We study the phase transition between pion condensed phase and normal phase, as well as chiral phase transition in a two flavor(\begin{document}${\cal{N}}_f=2$\end{document}) IR- improved soft-wall AdS/QCD model at finite isospin chemical potential \begin{document}$\mu_I$\end{document} and temperature T. By self-consistently solving the equations of motion, we obtain the phase diagram in the plane of \begin{document}$\mu_I$\end{document} and T. The pion condensation appears together with a massless Nambu-Goldstone boson \begin{document}$m_{\pi_1}(T_c, \mu_I^c)=0$\end{document}, which is very likely to be a second-order phase transition with mean-field critical exponents in small \begin{document}$\mu_I$\end{document} region. When \begin{document}$T=0$\end{document}, the critical isospin chemical potential approximates to vacuum pion mass \begin{document}$\mu_I^c \approx m_0$\end{document}. The pion condensed phase exists in an arched area and the boundary of the chiral crossover intersects the pion condensed phase at a tri-critical point. Qualitatively, the results are in good agreement with previous studies from Lattice simulations and model calculations.
Investigation of neutron density distribution of 208Pb nucleus when the proton density is constrained to its experimental distribution
A. R. Abdulghany
Published:   , doi: 10.1088/1674-1137/44/8/084103
In this study, two novel improvements for the theoretical calculation of the neutron distributions are presented. First, the available experimental proton distributions are used as a constraint rather than inferred from the calculation. Second, the recently proposed distribution formula, d3pF, is used for the neutron density, which is more detailed than the usual shapes, for the first time in nuclear structure calculation. A semi-microscopic approach for binding energy calculation is considered in this study, however, the proposed improvements can be introduced to any other approach. The ground state binding energy and neutron density distribution of 208Pb nucleus are calculated by optimizing the binding energy considering three different distribution formulae. The implementation of the proposed improvements leads to a qualitative and quantitative improvement in the calculation of the binding energy and neutron density distribution. The calculated binding energy agrees with the experimental value, and the calculated neutron density shows fluctuations within the nuclear interior, which agrees with the predictions of self-consistent approaches.
Investigation of rare semileptonic Bc→(D(s,d)(*))μ+μ- decays with non-universal Z′ effect
P. Maji, S. Mahata, P. Nayek, S. Biswas, S. Sahoo
Published:   , doi: 10.1088/1674-1137/44/7/073106
In this paper, we analyze different decay observables of semileptonic decays \begin{document}${B}_{c}\to \left({D}_{s,d}^{\left(*\right)}\right){\mu }^{+}{\mu }^{-}$\end{document} such as branching ratio, forward-backward asymmetry, polarization fraction and lepton polarization asymmetry in the non-universal \begin{document}$ Z'$\end{document} model. We have also studied the dependence of branching fraction to the new model parameters. Here, we have found that the values of different decay parameters increase in the \begin{document}$ Z'$\end{document} model, which provides a possible way out for the search of new physics as well as the unknown phenomena of charm B meson.
Electron and positron spectra in the three-dimensional spatial-dependent propagation model
Zhen Tian, Wei Liu, Bo Yang, Xue-Dong Fu, Hai-Bo Xu, Yu-Hua Yao, Yi-Qing Guo
Published:   , doi: 10.1088/1674-1137/44/8/085102
The spatial-dependent propagation (SDP) model has been demonstrated to account for the spectral hardening of both primary and secondary Cosmic Rays (CRs) nuclei above about 200 GV. In this work, we further apply this model to the latest AMS-02 observations of electrons and positrons. To investigate the effect of different propagation models, both homogeneous diffusion and SDP are compared. Different from the homogeneous diffusion, SDP brings about harder spectra of background CRs and thus enhances background electron and positron fluxes above tens of GeV. Thereby the SDP model could better reproduce both electron and positron energy spectra when introducing a local pulsar. The influence of background source distribution is also investigated, in which both axisymmetric and spiral distributions are compared. We find that taking account for the spiral distribution lead to a larger contribution of positrons for energies above multi-GeV than the axisymmetric distribution. In the SDP model, when including a spiral distribution of sources, the all-electron spectrum above TeV energies is thus naturally described. In the meantime, the estimated anisotropies in the all-electrons spectrum show that in contrary to the homogeneous diffusion model, the anisotropy under SDP is well below the observational limits set by the Fermi-LAT experiment, even taking a local source into account.
The Uplifting of AdS type to Quintessence Like Potential Induced by Frozen Large Scale Lorentz Violation
Hanyu Zhai, Jiayin Shen, Xun Xue
Published:   , doi: 10.1088/1674-1137/44/8/085101
The quintessence-like potential of vacuum energy can meet the requirement from both quantum gravity and the accelerating expansion of the universe. The anti-de Sitter vacuum in string theory has to be lifted to the meta-stable de Sitter vacuum with positive vacuum energy density to explain the accelerating expansion of the universe. Based on the possible large scale Lorentz violation, we define an effective cosmological constant which depends not only on the bare cosmological constant but also on the Lorentz violation effect. We find the evolution of the effective cosmological constant exhibits the behavior of quintessence potential when the bare cosmological constant is from string landscape in contrary to the existence of local minimum during evolution while the bare cosmological constant is supplied by the swampland. The critical value of bare cosmological constant is approximately zero for the behavior transition. The frozen large scale Lorentz violation can uplift the AdS vacua to an effective quintessence-like one in this sense.
Effective charge from lattice QCD
Z.-F. Cui, J.-L. Zhang, D. Binosi, F. De Soto, C. Mezrag, J. Papavassiliou, C. D. Roberts, J. Rodríguez-Quintero, J. Segovia, S. Zafeiropoulos
Published:   , doi: 10.1088/1674-1137/44/8/083102
Using lattice configurations for quantum chromodynamics (QCD) generated with three domain-wall fermions at a physical pion mass, we obtain a parameter-free prediction of QCD's renormalisation-group-invariant process-independent effective charge, \begin{document}$\hat\alpha(k^2)$\end{document}. Owing to the dynamical breaking of scale invariance, evident in the emergence of a gluon mass-scale, \begin{document}$m_0= 0.43(1)\;$\end{document}GeV, this coupling saturates at infrared momenta: \begin{document}$\hat\alpha(0)/\pi=0.97(4)$\end{document}. Amongst other things: \begin{document}$\hat\alpha(k^2)$\end{document} is almost identical to the process-dependent (PD) effective charge defined via the Bjorken sum rule; and also that PD charge which, employed in the one-loop evolution equations, delivers agreement between pion parton distribution functions computed at the hadronic scale and experiment. The diversity of unifying roles played by \begin{document}$\hat\alpha(k^2)$\end{document} suggests that it is a strong candidate for that object which represents the interaction strength in QCD at any given momentum scale; and its properties support a conclusion that QCD is a mathematically well-defined quantum field theory in four dimensions.
Transverse Ward-Takahashi Identities and Full Vertex Functions in Different Representations of QED3
Cui-Bai Luo, Hong-Shi Zong
Published:   , doi: 10.1088/1674-1137/44/7/073105
We firstly derive the transverse Ward-Takahashi identities (WTI) of N-dimensional quantum electrodynamics by means of the canonical quantization method and the path integration method, and then try to prove that QED3 is solvable based on the transverse WTI and the longitudinal WTI, that is, the full vector and tensor vertices functions can be expressed in term of the fermion propagators in QED3. Further, we discuss the effect of different γ matrix representations on the full vertex function.
Heavy flavor dissociation in the framework of multi-body Dirac equations
Shuzhe Shi, Jiaxing Zhao, Pengfei Zhuang
Published:   , doi: 10.1088/1674-1137/44/8/084101
We study heavy flavor properties at finite temperature in the framework of a relativistic potential model. With an improved method to solve the three-body Dirac equation, we determine a universal set of model parameters for both mesons and baryons by fitting heavy flavor masses in vacuum. Taking heavy quark potential from lattice QCD simulations in hot medium, we systematically calculate heavy flavor binding energies and averaged sizes as functions of temperature. The meson and baryons are separately sequentially dissociated in the quark-gluon plasma, and the mesons can survive at higher temperature due to the stronger potential between quark-antiquark pairs than that between quark-quark pairs.
Re-visiting Supersymmetric Janus Solutions: A Perturbative Construction
Nakwoo Kim, Se-Jin Kim
Published:   , doi: 10.1088/1674-1137/44/7/073104
We construct holographic Janus solutions, which describe a conformal interface in the theory of M2-branes, in four-dimensional gauged supergravities using a perturbative method. In particular, we study three Einstein-scalar systems and their BPS equations, which are derived by Bobev, Pilch, and Warner (2014) [1]. The actions of our interest are all consistent truncations of \begin{document}$ D = 11 $\end{document} supergravity chosen to be invariant under \begin{document}$ SO(4)\times SO(4) $\end{document}, \begin{document}$ SU(3)\times U(1)\times U(1) $\end{document}, and \begin{document}$ G_2 $\end{document} symmetry subgroups of \begin{document}$ SO(8) $\end{document} respectively. The utility of our semi-analytic result is illustrated by the calculation of minimal area surface and the associated holographic entanglement entropy.
Redshift drift in uniformly accelerated reference frame
Zhe Chang, Qing-Hua Zhu
Published:   , doi: 10.1088/1674-1137/44/5/055101
We construct an alternative uniformly accelerated reference frame based on 3+1 formalism in adapted coordinate. It is distinguished with Rindler coordinate that there is time-dependent redshift drift between co-moving observers. The experimentally falsifiable distinguishment might promote our understanding of non-inertial frame in laboratory.